Object fade out while going from point A to B in animation
Add a Mix shader connected to


your material
a 100% white Transparent BSDF shader

Then keyframe the Mix factor ("Fac:"): 


set it to 0.00 when you want the fading effect to start. Then, having your pointer over the value input, hit I (the box becomes yellow) 
then move to the frame where you want the fading out effect to be completed. Set the value to 1.00 and hit I again.





If you want to make the "Fac:" dependent on the distance from another object (an Empty representing point "B"), you can use drivers as in the answer to this question: Cycles Node to tell Distance from an Empty